CORESTA Congress, Shanghai, 2008, SSPT 01

Market survey of the mutagenicity, cytotoxicity and genotoxicity of smokeless tobacco products sold in Canada

Labstat International Inc., Kitchener, ON, Canada
This investigation was undertaken to characterize the range of toxicological responses for the majority of smokeless tobacco (ST) products sold in Canada. A total of 31 ST products were extracted with DMSO (1:9, w/v), in triplicate. These were tested for mutagenicity using the Ames assay using Salmonella typhimurium strains TA98, TA100, TA102, TA1535 & TA1537 with S9 activation. In addition, a subset of 12 DMSO extracts was tested for cytotoxicity (neutral red uptake (NRU) assay) and genotoxicity ( in vitro micronucleus (MN) assay). A subset of 4 ST products was also extracted with (i) dichloromethane (DCM) and (ii) artificial saliva (AS). With one exception, all of the 31 DMSO ST extracts were very similar in their mutagenic activity. The greatest response was observed from strains TA100 and TA102 with slight TA98 activity. The maximum activity (TA100) was 30 revertants/mg extracted ST, which is about 3% of that observed for extracts of 'tar' prepared from KR2R4F and greater than that observed from DCM and AS extracts. Cytotoxicity (IC50) of the 12 DMSO extracts ranged from 380 to 8850 µg ST/mL media in contrast to 54 µg/mL observed for KR2R4F 'tar' extracts. When grouped by product type, the order of cytotoxicity was Gutka>Snuff>Pouch>Plug>Long Cut. For most brands, DCM and AS extractants exhibited little or no cytotoxic activity. There was some evidence for a difference in genotoxicity among the 12 ST products; the genotoxicity of DMSO extracts of Gutka and Snuff (combined) being lower than the combined result for Plug, Pouch and Long Cut (averages 0.282 vs. 0.587% MN/mg ST/mL media). However the maximum response was only 7% of that determined for KR2R4F 'tar' extracts. DMSO, DCM and AS extracts were similar in genotoxic activity with the exception of Gutka where the order was AS>DCM>DMSO.